Airbag is installed in an automobile for rapidly inflating to a flexible envelope in a car crash to prevent vehicle occupants from striking interior objects such as the steering wheel or a window. Modern vehicles may contain multiple airbags in various side and frontal locations of the passenger seating positions and sensors may deploy one or more airbags in an impact zone at variable rates based on the type and severity of impact. Frontal airbags for driver and passenger are generally made of uncoated fabrics while the side and side curtain airbags are made of coated fabrics with low air permeability for side impact.
With advent of computing technologies, airbag is designed using computer aided engineering analysis (e.g., a finite element analysis (FEA). Membrane finite elements have been used for representing airbags. While this technique works for simulating airbags made of uncoated fabric, it does not work well for coated fabric. The reason is because membrane elements do not possess any bending stiffness or resistance provided by coated fabric. As a result, the simulated airbag has higher tendency of folding when membrane elements are used.
In prior approaches, either conventional shell finite elements with modifications to bending terms or adding a weak shell element to each membrane element to capture the additional bending resistance of coated fabric is used. Neither of these prior art approaches is satisfactory because significant computation time (e.g., doubling the amount of computation costs of a membrane element model) are required thereby prolonging design process and increasing the costs.
It would therefore be desirable to have more efficient methods and systems for numerically simulating structural behaviors of airbag made of coated fabric material.